1. Field of the Invention
This invention relates to an apparatus and a method for measuring the accuracy of a mirror surface of a reflecting mirror antenna or the like which are mounted on a satellite.
2. Description of the Prior Art
An example of apparatus of this type in the prior art is shown in FIG. 1. The arrangement shown in FIG. 1 is disclosed in the "Antenna Engineering Handbook" edited by the Japanese Institute of Electronics, Information and Communication Engineers, p. 458, Jun. 20, 1988, published by OHM Co., Ltd. In FIG. 1, the numeral 1 denotes an antenna, 2 denotes a theodolite for measuring the mirror surface of the antenna by the triangulation method, and 3 denotes a controller for measuring the mirror surface with the theodolite 2.
The operation of the apparatus shown in FIG. 1 is as follows: The antenna 1 is fixed in a horizontal position so that the mirror surface of the antenna can be seen from the theodolites 2. A plurality of theodolites 2 face to the mirror surface from different positions and measure the configuration of the mirror surface in the three-dimensional coordinates system. A controller 3 controls the theodolites 3 to automatically measure points on the mirror surface directed by the theodolites and record the measured results. Therefore, the configuration of the mirror surface can be measured in the three-dimensional coordinates system.
Another apparatus of this type in the prior art is shown in FIG. 2. This arrangement is also described in the "Antenna Engineering Handbook" edited by the Japanese Institute of Electronics, Information and Communication Engineers, p. 449, published by OHM Co., Ltd. on Jun. 20, 1988. In FIG. 2, the numeral 4 denotes a probe for measuring the electric field distribution in the vicinity of antenna 1, 5 denotes a scanner for plane-scanning the probe 4, and 6 denotes a transceiver. The beam axis of the antenna 1 is defined as the axis z, and thereby the coordinates associated with the antenna are defined as the x-y-z orthogonal coordinates system and the coordinates associated with the scanner as the X-Y-Z orthogonal coordinates system. Moreover, the antenna 1 is placed so that the x-y plane and X-Y plane are parallel. With the arrangement, the electric field distribution in the vicinity of the antenna is measured and the deviation from the phase distribution of the ideal mirror surface is obtained from the measured phase distribution, thereby an error of the mirror surface can be obtained.
Since conventional antenna mirror surface measuring apparatuses were constituted as explained above, the measurement was made under the condition that an antenna is deformed by the influence of-the gravity. Accordingly, here rises a problem that the intrinsic deformation of the mirror surface in such a condition that a satellite is set on an orbit, namely under the zero-gravity condition cannot be separated from the deformation due to the gravity.